On LinkedIn (and similar professional sites), you can connect with people you might never meet otherwise. If you have used LinkedIn for many years, you may find that some of those connections are very weak: in fact, you may have forgotten when and why you agreed to become contacts.
How long should you keep those weak connections? Should you purge your contact list, keeping it for your closest and most active connections?
I disagree with purging, unless a connection has spammed you or has done something else unethical. You never know when a connection might become critical for your job search.
Even though I changed industries years ago (I was a chemical engineer), many of my connections from that time have reached out to me through LinkedIn, and we have reconnected on a personal and business basis.
For example, one subcontractor who has now worked for me for years first came to my attention in an entirely other capacity when we worked together 25 years ago. We reconnected through LinkedIn. Had I purged my list when I changed careers, we may not have reconnected. I also generate business through my connections and help my clients.
Why would I disconnect anyone? Just because someone is inactive today, does not mean they will be inactive tomorrow. As a professional resume writer, I’ve found that all connections are valuable during a job search.